<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <img src="images/s.gif" alt="">
    <div>上午好</div>
    <script src="js/public.js"></script>
    <script>
        var img = $('img')
        var div = $('div')
        var date = new Date()
        var h = date.getHours()
        if (h < 12) {
            img.src = 'images/s.gif'
            div.innerHTML = '上午好'
        } else if (h < 18) {
            img.src = 'images/x.gif'
            div.innerHTML = '下午好'
        } else {
            img.src = 'images/w.gif'
            div.innerHTML = '晚上好'
        }
    </script>
</body>

</html>